The components of the insulin receptor have been examined using SDS polyacrylamide gel electrophoresis for the IM-9 lymphocyte receptor and using radiation inactivation for the rat liver membrane receptor. The results from radiation inactivation studies suggest that the insulin receptor is composed of at least two components. One component appears to be a high molecular weight affinity-regulator of a second component the insulin binding component, which appears to have a lower molecular weight. Computer analysis of these results indicate a possible model for the insulin receptor would be a polymer of binding components plus affinity-regulatory components.